The Biosynthesis of Homarine and N-methyl Quinolinate in Marine Crustacea will be continued using Shrimp Muscle Homogenates. The condensation of glycine with succinyl CoA to form N-succinyl glycine appears to be the first step in homarine biosynthesis. This reaction will be studied further in an attempt to evaluate this mechanism for biosynthesis of pyridine rings. Transmethylation by homarine appears to be significant and will be investigated further. The biosynthesis of quinolinate from aspartic acid and appropriate 3-carbon precursors will be further studied. Since quinolinate is readily methylated to N-methyl quinolinate, its role as methyl donor and its catabolic fate will be investigated along with homarine catabolism.